Many surgical procedures require vessels or other tissues of the human body to be ligated during the surgical process. For example, many surgical procedures require cutting blood vessels (e.g., veins or arteries), and these blood vessels may require ligation to reduce bleeding. In some instances, a surgeon may wish to ligate the vessel temporarily to reduce blood flow to the surgical site during the surgical procedure. In other instances a surgeon may wish to permanently ligate a vessel. Ligation of vessels or other tissues can be performed by closing the vessel with a ligating clip, or by suturing the vessel with surgical thread. The use of surgical thread for ligation requires complex manipulations of the needle and suture material to form the knots required to secure the vessel. Such complex manipulations are time-consuming and difficult to perform, particularly in endoscopic surgical procedures, which are characterized by limited space and visibility. By contrast, ligating clips are relatively easy and quick to apply. Typically, a clip is applied to the vessel or other tissue by using a dedicated mechanical instrument commonly referred to as a surgical clip applier, ligating clip applier, or hemostatic clip applier. Accordingly, the use of ligating clips in endoscopic as well as open surgical procedures has grown dramatically.
Ligating clips can be classified according to their geometric configuration (e.g., symmetric clips or asymmetric clips), and according to the material from which they are manufactured (e.g., metal clips or polymeric clips). Symmetric clips are generally “U” or “V” shaped and thus are substantially symmetrical about a central, longitudinal axis extending between the legs of the clip. Symmetric clips are usually constructed from metals such as stainless steel, titanium, tantalum, or alloys thereof. By means of a dedicated clip applier, the metal clip is permanently deformed over the vessel. An example of one such clip is disclosed in U.S. Pat. No. 5,509,920 to Phillips et al. An example of a metallic clip applier is disclosed in U.S. Pat. No. 3,326,216 to Wood in which a forceps-type applier having conformal jaws is used to grip and maintain alignment of the clip during deformation. Such appliers may additionally dispense a plurality of clips for sequential application, as disclosed in U.S. Pat. No. 4,509,518 to McGarry et al.
With the advent of high technology diagnostic techniques using computer tomography (CATSCAN) and magnetic resonance imaging (MRI), metallic clips have been found to interfere with the imaging techniques. To overcome such interference limitations, biocompatible polymers have been increasingly used for surgical clips. Unlike metallic clips, which are usually symmetric, polymeric clips are usually asymmetric in design and hence lack an axis of symmetry. Inasmuch as the plastic clip cannot be permanently deformed for secure closure around a vessel or other tissue, latching mechanisms have been incorporated into the clip design to establish closure conditions and to secure against re-opening of the vessel. For example, well known polymeric clips are disclosed in U.S. Pat. No. 4,834,096 to Oh et al. and U.S. Pat. No. 5,062,846 to Oh et al., both of which are assigned to the assignee of the presently disclosed subject matter. These plastic clips generally comprise a pair of curved legs joined at their proximal ends with an integral hinge or heel. The distal ends of the curved legs include interlocking latching members. For example, the distal end of one leg terminates in a lip or hook structure into which the distal end of the other leg securely fits to lock the clip in place.
The distal ends of the clips taught in U.S. Pat. No. 5,062,846 to Oh et al. also include lateral bosses that are engaged by the jaws of a clip applier. A clip applier specifically designed for asymmetric plastic clips is used to close the clip around the tissue to be ligated, and to latch or lock the clip in the closed condition. In operation, the jaws of this clip applier are actuated into compressing contact with the legs of the clip. This causes the legs to pivot inwardly about the hinge, thereby deflecting the hook of the one leg to allow reception therein of the distal end of the other leg. A clip applier designed for use with asymmetric plastic clips in an open (i.e., non-endoscopic) surgical procedure is disclosed in U.S. Pat. No. 5,100,416 to Oh et al., also assigned to the assignee of the presently disclosed subject matter.
In addition to compatibility with sophisticated diagnostic techniques, asymmetric clips have other advantages over symmetric clips. For example, because asymmetric clips are formed from polymeric materials, the mouths of asymmetric clips can generally be opened wider than the mouths of symmetric clips. This allows a surgeon to position the clip about the desired vessel with greater accuracy. In addition, a clip of the type described in the aforementioned U.S. Pat. Nos. 4,834,096 and 5,062,846 can be repositioned before locking the clip on the vessel or before removing the clip from the vessel, in a process referred to as “approximating” the clip.
Various types of hemostatic and aneurysm asymmetric clips are used in surgery for ligating blood vessels or other tissues to stop the flow of blood. Such clips have also been used for interrupting or occluding ducts and vessels in particular surgeries such as sterilization procedures.
Applying the clip for occluding the vessel or other tissue might be the end desired result. Generally then, the clip is left in place after application to the tissue until hemostasis or occlusion occurs. At some point thereafter, the clip can be removed by using a separate instrument dedicated for that purpose, i.e., a clip removal instrument.
However, in many procedures, a vessel is occluded so that it can be safely cut. In this type of procedure, generally a vessel is clamped on both sides of the desired cut site and then the vessel is severed between the two clips. The vessel can then be anastomosed at the cut ends, or to other vessels or tissue, as required by the particular procedure. After anastomosis, the clips can be removed to restore circulation through the tissue.
Whether the clip is metallic or polymeric, it is important to leave a small cuff of tissue, typically about 1.0-3.0 mm, between the cutting face of the clip and the cut site. Without a cuff, the clip might not properly stay attached or secured in place on the vessel. For instance, the tissue could retract after cutting and pull out of the clip. Also, if the clip is applied askew, an end could pull out, resulting in leakage from the cut vessel. Further, cutting too close to the clip risks the clip being accidentally nicked, which could result in failure of the clip.
Although physicians generally desire to leave tissue cuffs on the cutting face of clips, certain situations can make this difficult. For example, in surgical sites with limited space, such as in endoscopy, the cutting zone can be very narrow, thus resulting in the placement of the clips too close to one side or the other of the cut site. Also, instances where the physician desires to preserve as much vessel as possible on the uncut face of the clip, can result in placement of the clip too close to the cut site. Finally, in close or obstructed-view surgical sites, judging the proper distance to cut from the clip can be extremely difficult.
Although polymeric ligating clips are well known in the surgical area and improvements have been made to the ligating clips, none have heretofore been designed with a mechanism to aid the physician in cutting ligated tissue properly, so that a safe length of tissue cuff remains on the cutting face of the clip. Therefore, there is believed to be a long-felt need for an improved polymeric surgical ligating clip with such a mechanism, which is particularly well suited for use in guiding a physician when cutting ligated tissue. The present disclosure is believed to provide such an improved surgical clip.